The officials have said the death toll has climbed at least four people while at least 32 others have sustained injuries and are undergoing treatment in the District Headquarter Hospital in Bannu.

Haroon Bilour, a senior secular politician and candidate for a provincial assembly seat, was among those killed in Tuesday's bombing. Thousands flocked to his funeral the next day.

The MMA is a coalition of religious parties based in Pakistan's northwest. "Saddened to learn of Nawabzada Siraj Raisini's shahadat in this targeted attack as well as the shahadat of 15 other innocent citizens".

"What credibility will these elections have when the government is taking such a drastic action against our people and this crackdown is taking place all over the country?" he told Reuters at the airport in Abu Dhabi as he waited for a connecting flight to Lahore.

The deadly attacks were condemned by President Mamnoon Hussain, Interim Prime Minister Nasirul Mulk, Army chief General Qamar Javed Bajwa, caretaker chief ministers of all provinces among other political leaders.

But security across the country has dramatically improved since government and military operations cleared large swathes of territory near the Afghan border in recent years. But analysts have long warned that the country has not tackled the root causes of extremism.